For many years power lines have been constructed using natural poles made from pressure-impregnated pine. Because of developments in modern forestry however there has been a drastic reduction in the availability of full-grown timber and hence also of natural poles having the requisite dimensions. Because of this poles of glued timer have been developed which are designed to replace natural poles. Examples of such designs are shown in DE No. 665 210, GB No. 745 540, FR No. 2 348 345 and WO No. 80/02709.
In spite of the urgent demand for glued poles and in spite of the fact that a plurality of glued pole designs have been produced in past years, the tubular glued timber pole has not as yet however been widely employed for power lines and similar demanding applications. One reason for this is that from the production viewpoint these poles give rise to a number of problems which have not been satisfactorily solved using available techniques. These problems concern both the jointing and the gluing of the individual sections, also the requisite impregnation of the glued construction.